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Progress Report-2002 |
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NOTICE |
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1. TITLE: Effect of Controlling Jointed
Goatgrass in Wheat Rotations in Nebraska in 2002 2. PERSONNEL: Gail A. Wicks, Gordon E. Hanson, and Gary W. Mahnken, University of Nebraska, 461 West University Drive, North Platte, NE 69101. 3. TIME LINE: Initiated 1996 to be completed 2003. We are on time. 4. ORIGINAL HYPOTHESIS: Jointed goatgrass (JGG) could be controlled using best weed and crop management practices used in winter wheat rotations. 5. SUMMARY OF PROGRESS: Initially in 1996, we overseeded with 200 JGG spiklets/m2 across all plots in 15 acres of a non-uniform JGG infestation. The three rotations, winter wheat-fallow (W-F), winter wheat-ecofallow corn-fallow (W-C-F, and winter wheat-ecofallow corn-corn-fallow (W-C-C-F) have been in place 6 years. After 6 years of data collection, the effects of crop rotations, winter wheat cultivars, and time of tillage are affecting JGG densities. Preventing weed growth after wheat harvest with herbicides and beginning tillage for fallow and corn production in April provided conditions suitable for more JGG seed germination before wheat planting than no-till in the wheat or corn stubble. This trend has been consistent. Wheat yields were equal between tillage and no-till except 1998 and 2002. In1998, JGG reduced yields 6 bu/A, but in 2002 no-till wheat yielded 4 bu/A more than wheat grown in a tilled seedbed. Tillage did not reduce corn yields following the ecofallow period in 1998 and 1999 because of timely rainfall, but yields were less than no-till in 1997, 2000, and 2001. In 2002, corn yields were zero because of drought.
Table 1. Main-effect treatment means for JGG joint density, biomass, heads, and joint production before wheat harvest and winter wheat height and yield in 2002 at North Platte, NE.a _____________________________________________________________________________ Jointed goatgrass Winter wheat Plants Biomass Heads Joints Height Test wt Yield _____________________________________________________________________________ Crop Rotation b no./m2 kg/ha no./m2 no./m2 inches lb/bu bu/A
C-C-F-W 0 0.02 0 0 26.4 c 57.4 b 36.7 b W-C-F-W 0 0.02 0 0 27.5 b 57.7 b 44.8 a F-W-F-W 0.02 0 0 0 28.5 a 59.1 a 46.5 a LSD (0.05) ns ns ns ns 0.9 0.5 2.9
Tillage timing before harvesting wheat in 2002 Tillage (05-01-02) 0 0.2 0 0 27 57.5 b 40 b No-tillage 0.01 0 0 0 28 58.7 a 45 a LSD (0.05) ns ns ns ns ns 0.42 2
Cultivar Pronghorn 0.02 0 0 0 30 a 59.3 a 43 a Alliance 0 0.02 0 0 27 b 58.1 b 44 a Vista 0 0 0 0 25 c 56.8 c 42 a LSD (0.05) ns ns ns ns 0.9 0.4 ns _____________________________________________________________________________ a JGG spikelets (200/m2) were seeded September 4, 1996. b W = winter wheat, C = corn, F = fallow.
Table 2. Wheat variety effect means for jointed goatgrass density in spring and at fall harvest, and crop yield, North Platte, NE, 2002.a _____________________________________________________________________________ Jointed goatgrass plants Crop yield Spring 2002 (April 5) Fall 2002 (Sep. 19) _____________________________________________________________________________ Rotation b Prongc Alli Vista Prong Alli Vista Prong Alli Vista __________________________________ __________________________________________ --------------- no./m2 ------------- --------------- no./m2 ------------- ------ Height, inches ----- In corn F-W-C d 0 0 0 0.2 1.7 0.6 38 a 36 abc 36 ab F-W-C-C 1.0 0.9 1.4 426 395 320 34 bcd 33 cd 33 d C-F-W-C 0.1 0.2 0.03 0 0 0 29 e 28 e 28 eMean 0.4 0.4 0.5 142 132 107 34 x 32 x 32 x
In wheat bu/A W-F-We 0.2 0 0 1.5 1.4 2.0 46 a 47 a 46 a C-F-W 0 0.2 0 0 0.03 0 45 a 46 a 43 a C-C-F-W 0.4 0.2 0.1 0 0 0 37 b 38 b 36 bMean 0.2 0.13 0.03 0.5 x 0.5 x 0.7 x 43 x 44 x 42 x
In fallow F-W-F f 5.8 8.2 8.9 843 a 1050 a 1004 a W-C-F 0.4 1.7 0.8 0 b 0 b 0 b W-C-C-F 2.7 3.5 6.3 0.05 b 0 b 0 bMean 2.9 4.4 5.3 281 x 350 x 335 x ____________________________________________________________________________ a Numbers followed by the same letter within rows and columns in blocks are not significant at the 0.05 level. b W = winter wheat, C = corn, F = fallow. The first letter indicates the crop or fallow sequence in 2002. c Wheat cultivars: Prong = Pronghorn, Alli = Alliance, Vista = Vista. d This is the corn phase, because of drought corn heights were measure July 16. e This is the wheat phase so grain yields are wheat. JGG counts are in wheat or corn stubble in spring and seedlings in wheat or corn in the fall. f This is the fallow phase, no grain yields.
Table 3. Effect of post-wheat harvest weed management in ecofallow on jointed goatgrass density in spring and fall and crop yield, North Platte, NE, 2002.a _____________________________________________________________________________
Jointed goatgrass plants Crop yield Spring 2002 Fall 2002 _____________________________________________________________________________ Rotation b Tillage No-till Tillage No-till Tillage No-till ____________________________________________________________________________ ------ no./m2 -------------- --------no./m2 -------- Height, inches In corn F-W-C c 2.2 0.02 60 b 720 a 32 c 35 b F-W-C-C 0.02 0.2 0 c 0 c 28 d 29 d C-F-W-C 0 0 0.02 c 1.6 c 34 b 40 a Mean 0.7 0.1 19 y 234 x 31 y 34 x
In wheat wheat bu/A F-W-F-Wd 0 0.04 0.1 3.2 a 46 a 47 a W-C-F-W 0 0 0 0.02 b 42 b 48 a C-C-F-W 0 0 0 0.03 b 38 c 40 b Mean 0 x 0.1x 0.03 y 1.16 x 40 y 45 x
In fallow W-F-W-F e 15.1 0.1 914 a 1017 a F-W-C-F 0 1.9 0 b 0 b W-C-C-F 0 8.3 0 b 0.03 bMean 5.0 3.4 72 y 299 x ____________________________________________________________________________ a Numbers followed by the same letter within rows and columns in blocks are not significant at the 0.05 level. b W = winter wheat, C = corn, F = fallow. The last letter indicates the crop or fallow sequence in 2002. All plots were treated with atrazine + glyphosate after wheat harvest. Tillage occurred on half of the corn and fallow plots in April. c This is the corn phase, because of drought corn heights were measured July 16 which was the maximum height for the F-W-C-C rotation. Corn tasseled in the no-till plots in other rotations. d This is the wheat phase so grain yields are wheat. Wheat cultivars: Prong = Pronghorn, Alli = Alliance, Vista = Vista. e This is the fallow phase, no grain yields. JGG counts are in wheat or corn stubble in spring and seedlings in wheat or corn in the fall. |
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